Development of Semicircular Tubular Coreless Linear Motor and Its Motion Control

This paper proposes a semicircular tubular linear synchronous motor called a “circular shaft motor” (CSM). A CSM can realize direct‐drive motion along the circumference of a circle. The design of the CSM is described. A magnetic field analysis was performed for the CSM model. The thrust characteristics of the prototype CSM system were measured in experiments. Angle control and force control were performed to demonstrate the utility of the developed CSM.     

Work of Fracture and Crack Healing in Glass

The work of fracture, γwoF, of a soda-lime-silica glass was determined as 5.5 J/m² in an inert atmosphere and 4.4 J/m² in air by using a short bar specimen with a chevron notch. The critical stress intensity factor K_IC calculated from γ_wof obtained in an inert atmosphere agreed with the value, 0.88 MN/m^3/2, determined by the indentation method. In unloading-loading cycles during stable crack growth, crack healing was observed both on the diagram of load vs load-point displacement and visually. Crack healing is more prevalent in an inert atmosphere, occurring only minimally in air. The energy for healing was measured as 0.65 J/m² in an inert atmosphere and ∼0.21 J/m² in air.     

Numerical Fracture Analysis of Chevron-Notched Specimens: 11, Stability Condition for Crack Growth

Stability conditions for crack growth were studied in chevronnotched specimens with vacious kinds of geometry. The generalized Gibbs free energy G (α) for crack growth in a system composed of a specimen and a testing machine was theoretically considered and analyzed numerically using the results obtained in Part I. We emphasize in both works the importance of the surface boundary effect on the interlaminar shear correction factor k and show that G (α) varies discontinuously with the crack growth if Bluhm's assumption is applied. In addition to the geometric effects on the stability of crack growth, the influence of the testing machine's compliance was considered.     

R-Curve Behavior of a Polycrystalline Graphite: Microcracking and Grain Bridging in the Wake Region

The contributions of nonlinear fracture processes both in the microcracking frontal process zone and in the following wake region and of grain bridging to crack-growth resistance parameters are discussed in terms of the R-curve behavior of an isotropic polycrystalline graphite. The R-curve behavior of the graphite is characterized by rapidly increasing values at the initial stage of crack extension (Δa≤1 to 2 mm) followed by a steady-state plateaulike region and then a distinct decrease when the primary crack tip approaches the end surface of the test specimen. Scanning electron microscopy of fracture mechanics specimens revealed a dominant role of grain bridging in the following wake regions on the rising R-curve behavior and confirmed the significant size effect of the large-scale microcracking process zone on the falling R-curve behavior. The stress-derived fracture toughness (K_R) and the energy fracture toughness (R_c) are discussed in relation to the micro-cracking residual strain.     

MIXER VISCOMETRY to CHARACTERIZE FLUID FOODS WITH LARGE PARTICULATES

Mixer viscometry is an effective means of characterizing fluids containing particulates. an interrupted helical screw impeller used to determine the flow behavior of fresh concrete was scaled‐down to analyze fluid foods with large particulates. the mixer viscometer constant was determined to be 1.6 rad^?1 by the matching viscosity method. Large particulate food materials successfully investigated in this study included cream corn, salsa, smooth pasta sauce and chunky pasta sauce. Apparent viscosity curves were constructed from torque and angular velocity data. Testing materials exhibited shear‐thinning behavior and temperature dependence. Analysis revealed K and n values ranging from 10.1 Pa sⁿ to 40.3 Pa sⁿ and 0.17 to 0.36, respectively. Regression control charts, based on apparent viscosity and average shear rate data were constructed for each product. A protocol is presented for producing and utilizing these charts as a statistical quality control tool for industry.     

Numerical Fracture Analysis of Chevron-Notched Specimens: I, Shear Correction Factor, k

Numerical analyses are developed in both short bar and 4-point bend bar cases to estimate the interlaminar shear correction factor k of chevron-notched specimens with various kinds of geometry. The values of k were calculated by comparing the specimen compliances of Bluhm's slice models with those of finite element models. We elucidated the effect of surface boundary on k and modified the Bluhm's assumption. The modification has a slight influence on compliance, but is substantial when considering the stress intensity factor and elastic stored energy at fracture load. The present results give a basis for further consideration of the fracture behavior of chevron-notched specimens. Part II is a discussion of the stability condition for crack growth of chevron-notched specimens using the present results.     

Energy Principle of Elastic-Plastic Fracture and Its Application to the Fracture Mechanics of a Polycrystalline Graphite

Utilizing loading-unloading procedures on the basis of nonlinear energy principles, an empirical method for evaluating the nonlinear fracture mechanics parameters, i.e. the nonlinear energy toughness G_c , the crack growth resistance R , the J_c value, and the plastic energy dissipation rate φ _p , was established. These parameters were experimentally determined for an isotropic polycrystalline graphite enabling the elastic-plastic fracture mechanics of graphite to he addressed. The graphite exhibits a typical elastic-plastic fracture with ×38% of the total fracture energy consumed as plastic energy. It was concluded that the widely used assumption of the applicability of linear elastic fracture mechanics to polycrystalline graphites can lead to erroneous results if the fracture tests are conducted with the usual specimen size. The proposed experimental method for evaluating elastic-plastic fracture parameters is potentially very effective for studying various nonlinear fractures in other ceramic materials.     

Microstructure formation and grain refinement of Mg-based alloys by electromagnetic vibration technique

The microstructure formation and grains refinement of two Mg-based alloys, i.e. AZ31 and AZ91D, were reported using an electromagnetic vibration （EMV） technique. These two alloys were solidified at various vibration frequencies and the microstructures were observed. The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover, the grain size distribution was outlined versus number fraction. A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state. The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid, which can activate melt flow. The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account. Moreover, the influence of the static magnetic field on texture formation is also considered, which plays an important role at higher vibration frequencies.     

A circular dichroism study of the effect of some organic solvents on the actomyosin of sardine (Sardinops melanosticta)

Circular dichroism (CD) was used to study changes in conformation of sardine ( Sardinops melanosticta ) actomyosin after treatment with some organic solvents. Untreated sardine actomyosin showed two negative bands at 208 and 222 nm, typical of proteins possessing α-helix configurations. The water-miscible alcohols methanol, ethanol, isopropanol and n-butanol, and the water-immiscible solvents n-hexane, n-octanol, and dichloromethane altered the native conformation of sardine actomyosin. The degree of alteration of native sardine actomyosin was principally dependent on the alcohol concentration and temperature used for dewatering. The least damage occurred with isopropanol, or with 10 or 90% aqueous ethanol; most damage occurred with 40–50% aqueous ethanol. Dichloromethane and n-butanol increased the α-helical content of the native protein. Treatment with hydrophilic and hydrophobic solvents at 70 and 20°C unfolded the protein to form a random coil, but defatting treatment at 2°C caused little damage.